queryUserByID method
Retrieve an array of third-party users from a Matrix User ID.
userid The Matrix User ID to look up.
Implementation
Future<List<ThirdPartyUser>> queryUserByID(String userid) async {
  final requestUri = Uri(
    path: '_matrix/client/v3/thirdparty/user',
    queryParameters: {
      'userid': userid,
    },
  );
  final request = Request('GET', baseUri!.resolveUri(requestUri));
  request.headers['authorization'] = 'Bearer ${bearerToken!}';
  final response = await httpClient.send(request);
  final responseBody = await response.stream.toBytes();
  if (response.statusCode != 200) unexpectedResponse(response, responseBody);
  final responseString = utf8.decode(responseBody);
  final json = jsonDecode(responseString);
  return (json as List)
      .map((v) => ThirdPartyUser.fromJson(v as Map<String, Object?>))
      .toList();
}